Kivy screen篇 ShaderTransition 講解

簡述

根據官方解釋:

Transition class that uses a Shader for animating the transition between 2 screens. By default, this class doesn’t assign any fragment/vertex shader.

意思是ShaderTransition是兩個Screen之間設置轉換動畫的類

基本範例

在main.py中寫上此段程式碼:

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen, ShaderTransition
from kivy.properties import ObjectProperty


class AScreen(Screen):
    pass


class BScreen(Screen):
    pass


class sm(ScreenManager):
    a1 = ObjectProperty(ShaderTransition(duration=3))


class MyApp(App):

    def build(self):
        return sm()


if __name__ == '__main__':
    MyApp().run()

在my.kv中寫上此段程式碼:

<AScreen>:
    name: 'menu'

    BoxLayout:

        Button:
            text: 'Goto settings'
            on_press: root.manager.current = 'settings'

        Label:
            text: str(root.transition_progress)


<BScreen>:
    name: 'settings'

    BoxLayout:

        Label:
            text: str(root.transition_progress)

        Button:
            text: 'still settings'
            on_press: root.manager.current = 'menu'


<sm>:
    transition: root.a1

    AScreen:

    BScreen:

執行結果如下:

由以上結果可以發現兩個Screen的轉換動畫為一片空白，因為我們並沒有指定轉換動畫為何。若想要有轉換動畫，可以用之前介紹的現成的Transition，或者研究fragment shaders語法並添加至ShaderTransition的fs參數(請容我跳過講解fragment shaders的概念與語法，這是另外一門程式語言)。